G77
Free Fortran 77 compiler using the GCC back-end.
url: www.gnu.org/software/fortran/fortran.html
G95
Ongoing project to create a free, open source Fortran 95 compiler and runtime libraries. Most of standard Fortran 77 is supported with some Fortran 90 and 95 features.
url: www.g95.org/
GNU Fortran 95
Ongoing project to develop a Fortran 95 compiler front end, as well as runtime libraries, for the GNU Compiler Collection (GCC).
url: gcc.gnu.org/fortran/